FAD-driven electrochemical system promises safer, cheaper green hydrogen storage

A research team affiliated with UNIST has unveiled a novel system to produce green hydrogen more cost-effectively by harnessing a biological energy coenzyme to reduce electrical energy consumption. This technology also enables direct storage of hydrogen within liquid organic compounds without the need for prior conversion into gas, promising substantial reductions in both production and transportation costs. The study is published in Applied Catalysis B: Environment and Energy.

Led by Professor Hyun-Kon Song in the School of Energy and Chemical Engineering at UNIST, the research team designed an electrochemical system that utilizes flavin adenine dinucleotide (FAD)—a coenzyme vital in cellular energy metabolism—to generate and immediately store hydrogen in liquid organic forms at low voltage.

The system features electrodes made of platinum (Pt) and palladium (Pd). During operation, formic acid (HCOOH) is oxidized on the platinum electrode, releasing electrons that travel to the palladium electrode, where hydrogen ions (H⁺) combine with these electrons to form atomic hydrogen (H*). This hydrogen then permeates through a palladium membrane directly into an attached liquid organic medium for storage.

By applying FAD to both electrodes, the team enhanced the efficiency of hydrogen production while significantly reducing the electrical energy needed. Notably, the cell operated effectively at an ultra-low voltage of approximately 0.6V—a reduction of about 65% compared to conventional systems.

The system also demonstrated remarkable durability, maintaining performance for more than 100 hours of continuous operation—eight times longer than typical setups—without degradation. This longevity is crucial, as higher operating voltages tend to increase power consumption and shorten device lifespan.

A key advantage of this technology is the elimination of the need for separate processes to compress or handle gaseous hydrogen. As explained by first author Jisu Lee, “Instead of producing hydrogen gas (H₂) and then pressurizing or reacting it further, our system directly stores hydrogen atoms (H) generated at the electrode surface into liquid organic compounds, simplifying the process and improving safety.”

FAD, a coenzyme naturally found in mitochondria to assist in energy production, possesses the unique ability to transfer both electrons and protons. In this system, it plays a tailored role: On palladium, it promotes hydrogen atom attachment to the electrode surface, while on platinum, it facilitates the removal of intermediate hydrogen species, ensuring smooth and efficient reactions on both sides.

Professor Song emphasized, “By integrating the electron and proton transport capabilities of biological molecules like FAD into electrochemical systems, we have simultaneously addressed hydrogen production and storage. This innovation offers a safe, efficient, and low-cost approach to hydrogen energy, without the need for high-pressure tanks.”